2023-06-30 04:00:00
Building a greenhouse on the roof to reduce CO2 emissions from buildings is a European study project carried out here. Useful for saving energy, it is also a means of producing food in the city. Tomorrow, will we see greenhouses multiplying on the roofs of cities to feed city dwellers?
Cédric Mosbeux is the owner of a restaurant in Brussels. A few months ago he removed Scottish salmon from his menu. This star fish is replaced by smoked trout raised in Brussels.
We have a fish that we trace from A to Z
“This salmon which crosses hundreds, even thousands of km to get here, then which still has to be processed in conditions which are not always optimal. Whereas here we have a fish which we trace from A to Z. We liked the long-term vision and especially the local focus of the product”confides the restaurateur.
This trout, Cédric buys it 3 kilometers from his restaurant. She grew up on the roofs of Anderlecht slaughterhouses.
More than a fish farm, it is an aquaponic farm. Deborah Lozano makes us discover this place. “We have a capacity of 20 tons per year”specifies the communication manager of this farm. “Our project was to demonstrate that it was possible to produce different types of food in the city, in particular shellfish and fish. And the aquaponic system that we have set up within the farm allows us to produce that”she continues.
Fish poop is used as a natural fertilizer for our plants
Next to the rearing ponds stands a greenhouse of 2,000 square meters where herbs and vegetables grow. 2 food productions that work in symbiosis.
“We produce hydroponically, so it’s not in conventional soil, it’s not in a field, in a garden. We need a substrate. The water from the fish farm is used as a substrate for our In this water, there is a mixture of fish farming water and effluent, so fish poo that we use as natural fertilizer for our plants.”explains Deborah Lozano.
Today, the sun is enough to bring the greenhouse to an ideal temperature for the growth of tomatoes. If it is too cold, the farm can rely on the heating system of the building below. “The greenhouse is fed by hot water that goes up to 70 degrees. And this water is heated by a heat pump system that is integrated into the building”says the communication manager.
Rooftop greenhouse production is very expensive
Tracking energy savings to limit costs is what Haïssam Jijakli, professor of urban agriculture at the University of Liège, studies.
On the roofs of the University of Gembloux, he participated in the construction of a greenhouse, the architecture of which alone saves 14% of energy. It will soon be connected to the laboratory cooling system. Machines that emit heat into the atmosphere. “In this way, we will be in balance at the energy level. When the greenhouse works, it does not need additional energy, just that which comes from the building and which already exists”.
Despite the energy savings, producing in a rooftop greenhouse is very expensive. This means you can’t grow just anything. Here we are testing mugwort, a plant used in the pharmaceutical industry.
A model exported to France
“If we work on this plant, it is because it has a very high added value, so it can be suitable for restricted spaces, as we find in town”emphasizes the professor.
Today in Belgium, entrepreneurs who start producing in greenhouses or on roofs are still looking for the best formula to ensure their profitability. The Anderlecht slaughterhouse farm exports its model to France. A project under construction that will not be installed on the roof: French trout will soon be swimming on the floor of the cows.
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